I think someone has confused pathological, compulsive, and effective lying. People generally lie because they have some apparent psychological motive or external benefit. In the case of the Heenes, their lies were part of a plan to sought to obtain a reality TV show about themselves. They had clear motives, psychologically they desired attention and financially they desired the revenues for TV show. Pathological lying is the exact opposite of this, pathological lies appear to be purposeless and in some cases, they are actually damaging to the liar. Pathological liars are actually bad liars, they are unable to convince others that their lies are true, the general point of a lie. This is generally thought to be a symptom of organic deficit in the brain. These people know what the truth but cannot tell it to others.

In contrast, compulsive lying is may a learned problem. Children who are punished for telling the truth or who see their parents lie successfully start to tell lies out of habit and example. These people also know the truth but simple have learned not to do so.

One of the reasons being an effective liar is difficult is that it does, as you note, require the liar to understand the truth and then construct a lie that the listener will believe. The lie, to be effective, must be personalized to the listener. A lie that will work for one person will not work for another. So it is difficult to tell a single lie, they tend to multiply and more and more people become involved. This is why the best lies are just half the truth.

The most effective liars are those who lie to themselves. After repeatedly lying to themselves, they come to actually believe their own lies. This usually takes a long time but with practice it may well take less. As some wit once noted “Why be a hypocrite when it is so easy to deceive yourself”. It would be interesting to see if this instrument would be able to pick out those sorts of lies.